The W(Alignment) widget controls the alignment and size of its
child widget. It has four settings: xscale, yscale, xalign, and
yalign.
The scale settings are used to specify how much the child widget
should expand to fill the space allocated to the W(Alignment). The
values can range from 0 (meaning the child doesn't expand at all)
to 1 (meaning the child expands to fill all of the available
space).
The align settings are used to place the child widget within the
available area. The values range from 0 (top or left) to 1 (bottom
or right). Of course, if the scale settings are both set to 1, the
alignment settings have no effect.
NOIMG
GTK.Adjustment()->set_value()